Pipe coupling

ABSTRACT

A connector for a composite pipe includes a male conical member to be inserted between inner and outer layers of the pipe. The outer layers have oppositely wound composite strips which are overlapped along the conical surface. The ends of the strips are braided and a cup located over the conical surface. A filler is injected between the cup and conical member to fill the voids formed between the overlapping strips.

The present invention relates to a connection for a tubular compositestructure.

In U.S. Pat. No. 5,261,462, there is described a tubular compositestructure which may be used as a flexible pipe. The structure shown inU.S. Pat. No. 5,261,462 is made up of a number of layers of helicallywound composite with elastomeric strip interposed between the successivepasses of the composites. A pair of layers are provided with radicalprojections that are located between a pair of elastomeric strips of anadjacent layer so that relative movement between the adjacent layers iscontrolled during bending.

The tubular structure shown in the above-noted U.S. patent has met withacceptance in the field and provides an effective alternative toconventional steel welded pipe. It is, however necessary to connect thecomposite structure to conventional fittings to facilitate itsinstallation in a practical environment.

In the above-noted U.S. patent, there is shown a method of connecting apair of tubular structures in end-to-end relationship by utilizing thehelically wound nature of the composite layers. The elastomeric stripsbetween the composite layers are removed and replaced with furthercomposite layers so that a strong connection could be obtained. It wasalso proposed in the prior patent that a similar process might beutilized with a coupling by providing helical recesses in the flange ofthe coupling and laminating the tubular structure to the coupling.

Such an arrangement has not been found satisfactory due to the high endloads that are imposed upon the flexible couplings and the tendency ofthe composite structure to unwind from the coupling when subjected topressure fluctuations. In general, it is found that the interfacebetween the flexible tubular structure and the end fitting should haveat least the same structural integrity as the flexible pipe itself andthat such a connection should be designed and tested to ensure that itequals or exceeds the maximum axial load in the pipe due totransportation and service loading. This axial load can result fromexternal axial tension or can be generated by internal pressure.

A common technique to connect an end fitting to a flexible pipe involvesswaging an outer wall of the fitting to trap the pipe wall betweenconcentric walls of the fitting. The mechanical interference providedresists axial loads and radial projections on the walls of fittingincrease the grip on the pipe wall. This technique relies upon theresilience of the pipe wall and so is not practical where relativelyrigid elements are use to fabricate the pipe wall.

An alternative technique is used with flexible pipe distributed byWellstream Corporation. Such pipe utilizes an interlocked steel carcassthat has limited axial movement between adjacent passes to allow limitedbending. Helically wound wire layers support the carcass. The wirelayers are wound in opposite hand and are laid over a reverse taper onthe fitting to secure the fitting. A cavity within the fitting is filledwith epoxy to hold the layers in situ and resist axial loads.

The use of the reverse taper introduces a spreading force on theoverlapping wires as an axial load is applied which tends to allow thewires to extrude from the fitting. Moreover, the initial increase indiameter necessary to provide the reverse taper introduces potentialslackness in the fitting that may permit an initial axial movement ofthe pipe relative to the fitting.

It is an object of the present invention to provide a connector thatobviates or mitigates the above disadvantages.

According to the present invention, there is provided in general terms aconnector for a multi-layered composite tubular structure in which acone member is inserted between adjacent layers of the tubularstructure. The radially outer layers of the structure are helicallywound in opposite directions over the conical outer surface of the cone.A female cone member is positioned over the radially outer surface ofthe outer layers and an axial force applied between the two cone membersto clamp the composite layers between their conical surfaces.

Preferably the layers are braided to one another at their distal end tomaintain structural integrity and as a further preference a wire isbraided into the strips to provide a circumferential band. A filler isapplied to the voids between the strips and conical surfaces. Thesurfaces are arranged so that axial forces applied to the pipe tend toreduce the volume of the voids and the filler thereby opposes suchreduction.

An embodiment of the invention will now be described by way of exampleonly with reference to the accompanying drawings, in which

FIG. 1 is a general side view of a tubular structure with the layersthereof progressively removed;

FIG. 2 is a section on the line 2--2 of the structure shown in FIG. 1;

FIG. 3 is a sectional view of the tubular structure of FIGS. 1-3incorporating a connector;

FIG. 4 is a side view showing a portion of the connector;

FIG. 5 is a view similar to FIG. 4 showing a subsequent stage in theformation of a connector;

FIG. 6 is a view portion of FIG. 4 on an enlarged scale; and

FIG. 7 is a view of the line 7--7 of FIG. 5.

FIGS. 1--2 show a tubular structure as exemplified in the above-notedU.S. patent and which will be described briefly to assist in theunderstanding of the present invention.

Referring therefore to FIG. 1, a tubular structure 10 has acircumferential wall 12 that is formed from a pair of juxtaposed wallelements 14,16. An outer sheath 18 completes the wall 12 and providesprotection from the environment for the elements 14,16.

As can best be seen in FIG. 2, the radially inner wall element 14comprises three separate layers, namely 20, 22 and 24. The inner layer20 consists of a continuous flexible plastic cylinder 26 having aspirally wound protrusion 28 projecting radially outwardly therefrom.The layer 20 can typically be formed from a thermoplastic polymer orelastomeric material and is preferably impermeable to the fluids towhich it may be exposed. Layer 20 may also act as an inner lineralthough a separate liner of impermeable material may be provided sothat the cylinder 26 may be formed from a material having differentproperties.

The outer layer 24 of the inner wall element consists of a spirallywound composite strip 30 having a radially inward projection 32 directedtowards the inner layer 20. The composite strip 30 has the same pitchand hand as the spiral projections 28. However, the projections 32 and28 are staggered axially and overlap in the radial direction.

A second spirally wound composite strip 34 is located between thesuccessive passes of the strip 30 and located axially so as to bealigned with the projection 28. Composite strips 30,34 each consist of abundle of fibres or roving, for example E-glass, generally orientated inthe direction of the winding with a matrix disbursed between the fibres.The strips may contain transverse fibres to resist secondary stressessuch as transverse shear, interlaminar shear, longitudinal shear, andcross fibre shear in the strip that are induced by internal pressure andin bending of the structure. The matrix may, for example, be polyester.Typically, the composite strips will have 75% by weight of fibre and 25%by weight of matrix although, as will be discussed more fully below,alternative materials and ratios may be used.

Located between the composite strips 30,34 are a pair of spirally woundelastomeric strips 36,38. These strips may be any suitable elastomersuch as neoprene. Strips 36 and 38 are located on opposite flanks of thecomposite strip 30 and act to maintain the composite strips 30 and 34 inspaced relationship.

An intermediate layer 22 is located between the layers 20,24 andconsists of a pair of composite spirally wound strips 40,42. Each ofthese strips 40,42 is of the same hand and same pitch as the strips 30and 34 and is axially located so as to overlap in the axial directioneach of the adjacent strips 30,34 in the outer layer 24. Each of thestrips 40 and 42 is located between adjacent ones of the projections32,28. A pair of elastomeric strips 44,46 and 48,50 is associated withthe composite strips 40 and 42 respectively and located on oppositesides thereof. Strip 44 is thus interposed between the composite strip40 and the projection 28 and elastomeric strip 46 is interposed betweenthe strip 40 and projection 32. Similarly, the elastomeric strips 48 and50 are interposed between the composite strip 42 and the projections 32and 28 respectively.

A layer of friction-reducing material such as polyethylene film 52 islocated between the inner layer 20 and intermediate layer 22. Similarly,a layer of friction-reducing material 54 is applied between the outerlayer 24 and intermediate layer 22 so as to minimize the resistance torelative movement between the layers 22 and 24.

Outer wall element 16 is separated from the inner wall element 14 by afriction-reducing film 56. The outer wall element 16 consists of innerand outer layers 58,60 which in turn are separated by afriction-reducing film 62. Each of the layers 58 and 60 consists ofalternating composite strips 64 and elastomeric strips 66 that arespirally wound. The pitch between successive passes of each strip 64 isgreater than that of the composite strips of the inner wall element 14so that in general there will be a greater number of individual strips64 than there are strips 30,34. For added clarity, each separate strip64 has been denoted with a suffix a,b in FIG. 3 with the correspondingelastomeric strip 66 also denoted with suffixes a, b and c. The pitch ofthe strips 64,66 in outer layer 60 of the outer wall element 16 is thesame as that of the inner layers 58. However the strips 64,66 in thelayer 60 are wound in an opposite hand to those in the layer 58 as canbe seen in FIG. 1.

A friction-reducing film 68 is located between the outer sheath 18 andthe layer 60 to minimize resistance to relative movement between thesheath and outer layer 60.

In operation, the principal bending stiffness of the structure 10 isdetermined by the flexible layer 20. The composite strips of the outerlayer 24 and intermediate layer 22 of wall element 14 essentiallyconstitute helical springs formed from composite material and do notcontribute significantly to the bending stiffness of the overallstructure. The overlapping of the composite strips of the intermediatelayer 22 and outer layer 24 provides a continuous barrier of compositemateial in a radial direction in the wall element 14 and therebysupports the layer 20 against internal pressure to inhibit extrusion ofthe layer 20 through the wall element 14. The elastomeric strips act tomaintain the composite strips uniformly distributed along the axiallength of the tubular structure and interact with the projections 28 and32 to maintain the composite strips 40,42 of the intermediate layercentred between the composite strips 30,34 of the outer layer 24.

As the tubular structure is flexed transverse to its longitudinal axis,the composite strips on one side of the natural axis move apart and thecomposite strips on the other side of the neutral axis move together.This is accommodated by a bodily displacement of the elastomeric stripswhich, however, maintain a uniform loading across the composite strip tomaintain them uniformly distributed and maintain the continuouscomposite barrier in the radial direction.

Further detail of the manufacture and performance of the tubularstructure may be found from prior U.S. patent and need not be describedfurther at this time.

In order to connect the pipe 10 to a conventional fitting it isnecessary to provide a connector that terminates the pipe and permits afitting to be attached to the pipe.

Referring therefore to FIG. 3, a connector generally indicated 100includes a male conical member 102 that has a radially outer conicalsurface 104 and an internal bore 106. The bore 106 has a thread 108 thatreceives a boss 110 of a flange 112. The conical member 102 is securedto the flange 112 by the thread 108 and boss 110. It may be welded ifpreferred.

Connector 100 also includes a cup 114 having a conical inner surface 116of similar included angle to the surface 104. The cup 114 terminates oneend in a flange 118 of similar diameter to the flange 112.

Each of the flanges 112,118 include holes 120,122 respectively toreceive studs 124. The holes 120 in flange 112 are threaded to engagethe studs 124 whereas the holes 122 in flange 118 provide a clearancefor the studs 124. Studs 124 project to the opposite side of flange 112to the cup 114 and so provide suitable attachment to a conventionalfitting 126 shown in ghosted outline.

An injection port 128 is provided in the male member 102 to allow afiller to be injected into the bore 106. Similarly, a port 130 isprovided in the cup 114 to allow a filler to be injected between theconical surfaces 104,116 of the male member and cupn respectively.

A shoulder 132 is formed on the surface 104 to provide acircumferentially extending recess and a similar undercut 134 is formedon the inner surface 116. The shoulders 132,134 define an annular recessindicated at 136 extending about the connector 100.

As shown in FIG. 3, the male member 102 is dimensioned to be insertedbetween two of the layers that collectively make up the wall elements14,16.

The bore 106 is dimensioned to receive the layers that make up the innerwall element 14. The inner layer 20 is welded to a stub end 142 at theseam 144. A radial web 146 on the stub end 142 extends across the faceof the flange 112 to provide a sealing face with the fitting 126. Acompression ring 148 inhibits extrusion of the web 146 as the fitting126 is tightened against flange 112.

The assembly of the connector 100 to the pipe 10 proceeds as followswith the dimensions recited being typical for a 2 inch internal diameterpipe:

1. The cup 114 is placed over the pipe (pipe end of the cup first) at adistance from the pipe end so that there is enough space for thesubsequent steps.

2. A hose clamp is tightened onto the pipe approximately 20 inches fromthe end for a pipe of 2 inch diameter.

3. The outer cover 18 is removed from the pipe end to the hose clamp.

4. The elastomer strips 66 of layer 60 are removed from the pipe end tothe hose clamp.

5. The composite strips 64 of layer 60 are peeled back from the pipe endto the hose clamp.

6. The exposed layer of polyethylene film 62 is removed from the pipeend to the hose clamp.

7. The elastomer strips 66 of layer 58 are removed from the pipe end tothe hose clamp.

8. The composite strips 64 of layer 58 are peeled back from the pipe endto the hose clamp.

9. The exposed layer of polyethylene film 56 is removed from the pipeend to the hose clamp.

10. Two inches is removed from the end of the inner wall element 14.

11. A half inch of layers 24 and 22 are removed to expose the innerliner 20.

12. The elastomer strips 36,38 of layer 24 are removed back to 15 inchesfrom the end of the pipe.

13. A minimum of 3 inches, and preferably up to 15 inches, ofpolyethylene film 54 is removed from the end of the pipe between layers24 and 22.

14. A minimum of 3 inches, and preferably up to 15 inches, of elastomerstrips 44,46,48,50 are removed from the end of the pipe in layer 22.

15. The cone 102 is slid over the inner wall element 14 as close aspossible to the hose clamp so that at least 21/2 inches of the innerwall element 14 is exposed behind the cone 102.

16. The stub end 142 is inserted through the threaded flange 112 andtrimmed so that it extends 3 inches beyond the threaded flange 112 whichis then positioned at the end of the pipe 10.

17. Both the stub end 142 and the pipe 10 are supported (at the exposedinner wall element 14 and the stub end 142 is fused to the exposed innerliner 20.

18. The flashing is removed from the seam 144.

19. The cone 102 is moved to the threaded flange 112 and screwed ontothe boss 110.

20. The hose clamp is removed and the composite strips 64 of layers 58and 60 of the outer wall element 16 are then wrapped onto the cone. Thestrips overlap to provide a diamond pattern, as shown in FIGS. 4,5, and6, and define voids between the adjacent layers.

21. The last 6 inches of the composite strips 64 at the flange end ofthe cone 102 are braided with one another such that each of thecomposite strips 64 of layer 58 passes repeatedly over, and then under,the composite strips 64 of layer 60.

22. A one sixteenth inch diameter steel wire 154 is braided togetherwith the composite strips 64 of layers 58 and 60 for a length of 1/2inch immediately behind the cone shoulder 132.

23. A one eighth inch diameter steel wire 152 is braided together withthe composite strips 64 for a length of 1/2 inch immediately behind theprevious braided steel wire.

24. The cup 114 is moved over onto the braided cone 102, and rotated sothat the cup vent hole 130 is 180° from the cone injection hole 128.

25. The cup 114 is tightened to the threaded flange 112 by studs 124.

26. The pipe is pretensioned to 1,000 pounds axial load.

27. A liquid thermosetting polymer resin such as epoxy or vinyl ester isinjected through the cone injection hole 128 into the void between thecup and the cone and the void between the cone and the linersimultaneously and allowed to cure.

The application of the composite strips to the conical surface 104 ofthe member 102 results in the strips overlapping and forming rhombicvoids 150. The bottom of each void is closed by the conical surface ofthe member 102 and the top closed by the surface 116 of the cup 114. Theprogressively increasing diameter of the surface 104 causes the volumeof the voids 150 to increase progressively toward the end of the pipe10. Accordingly, any relative movement between the pipe and theconnector results in a reduction of the volume of the voids which isresisted by the injected thermosetting polymer. The spaced conicalsurfaces 104,116 prevent the composite strips from expanding radially asan axial load is applied. The polymer used may typically be a vinylester such as that available from Dow Chemical under the trade name DOWDerakane 411 Vinyl Ester. Other thermosetting polymers including epoxiesor polyesters could be used or alternatively thermoplastic polymers suchas polyamide or polyethylene with a suitable melt temperature can beused.

The composite strips 64 of layers 58 and 60 are braided to one anotherfor their last six inches as shown in FIG. 4.

The braiding applied to the composite strips is best seen in FIGS. 5 and7, and includes a pair of circumferential bands 152,154 of braiding wirethat is interwoven with the braided layers of composite strips. Thebands 152,154 provide a mechanical abutment against the recess 136 andwith the braiding of the strips 58,60 binds the ends to one another toprevent the strips from unravelling or extruding from between thesurfaces.

The anchoring of the strips to one another and to the recess 136 alsofacilitates the fractional engagement of the composites against theconical surface as axial loads are applied to enhance further theretention of the pipe with the connector. With the anchoring of thestrips, an axial load tends to cause the strips to engage the conicalsurfaces as a band brake so that the greater the load, the greater thefrictional retention. It is contemplated that under certain conditions acylindrical surface could be used for the insert with sufficientfrictional engagement of the strips being provided from their mechanicalinterconnection and braiding.

In tests with a sample pipe, axial loads in the order of 60,000 lbs.have been accommodated.

We claim:
 1. A pipe assembly including a length of pipe and a connectorat one end thereof for connecting the pipe to a fitting, said pipehaving an inner layer and a plurality of outer layers with at least twoof the outer layers having respective helically wound composite stripsof opposite hand, said connector including a conical member, a flangefor connecting said conical member to said fitting a cup and a fastenerto interconnect said cup and conical member, said conical member beinginserted between said inner layer and said outer layers, said innerlayer being restrained by said fitting and said flange with saidcomposite strips extending across a conical outer surface of saidconical member and crossing over one another to define voids ofprogressively increasing volume toward said one end, said cup having aconical inner surface engageable with a side of said outer layersopposite to said conical member, said fastener applying an axial loadbetween said cup and said conical member to engage said outer layersindependently of said inner layer, said voids having a filler therein tooppose a change in volume and inhibit relative axial movement betweensaid pipe and said connector.
 2. A pipe assembly according to claim 1wherein ends of said composite strips are mechanically interconnected toone another.
 3. A pipe assembly according to claim 2 wherein said endsare braided to one another.
 4. A pipe assembly according to claim 3wherein one of said conical surfaces is formed with a circumferentialrecess to receive said braiding.
 5. A pipe assembly according to claim 2wherein said strips are mechanically interconnected by braiding wireextending circumferentially about said conical member.
 6. A pipeassembly according to claim 1 wherein said flange is threaded to saidconical fitting.
 7. A pipe assembly according to claim 1 wherein saidfastener extends between said flange and said cup.
 8. A pipe assemblyaccording to claim 7 wherein said fastener includes a plurality ofthreaded studs extending axially between and flange and said cup.
 9. Apipe assembly according to claim 8 wherein said studs project from saidflange in a direction opposite to said cup to provide an attachment foran adjacent fitting.
 10. A pipe assembly according to claim 1 whereinsaid inner layer includes a liner that extends through said flange andacross a face thereof opposite to said fitting and radially from theaxis of said pipe.
 11. A pipe assembly according to claim 10 wherein afiller is located between said inner layer and said conical member. 12.A pipe assembly according to claim 11 wherein said filler is hardenableafter insertion.
 13. A pipe assembly according to claim 12 wherein saidfiller is thermosetting polymer.
 14. A pipe assembly according to claim13 wherein said filler in said voids is thermosetting polymer.
 15. Apipe assembly according to claim 1 wherein said filler in said voids iscurable after insertion.
 16. A pipe assembly including a length of pipeand a connector at one end thereof for connecting the pipe to a fitting,said pipe having an inner layer and a plurality of outer layers with atleast two of the outer layers having respective helically woundcomposite strips of opposite hand, said connector including a conicalmember, a flange for connecting said conical member to said fitting acup and a fastener to interconnect said cup and conical member, saidconical member being inserted between said inner layer and said outerlayers, said inner layer being restrained by said fitting and saidflange with said composite strips extending across a conical outersurface of said conical member and crossing over one another to definevoids of progressively increasing volume toward said one end, said cuphaving a conical inner surface engageable with a side of said outerlayers opposite to said conical member, said fastener applying an axialload between said cup and said conical member to engage said outerlayers independently of said inner layer, said voids having a fillertherein to oppose a change in volume and inhibit relative axial movementbetween said pipe and said connector, wherein ends of said compositestrips are mechanically interconnected to one another, wherein said endsare braided to one another, and wherein one of said conical surfaces isformed with a circumferential recess to receive said braiding.
 17. Apipe assembly including a length of pipe and a connector at one endthereof for connecting the pipe to a fitting, said pipe having an innerlayer and a plurality of outer layers with at least two of the outerlayers having respective helically wound composite strips of oppositehand, said connector including a conical member, a flange for connectingsaid conical member to said fitting a cup and a fastener to interconnectsaid cup and conical member, said conical member being inserted betweensaid inner layer and said outer layers, with said composite stripsextending across a conical outer surface of said conical member andcrossing over one another to define voids of progressively increasingvolume toward said one end, said cup having a conical inner surfaceengageable with a side of said outer layers opposite to said conicalmember, said fastener applying an axial load between said cup and saidconical member to engage said outer layers independently of said innerlayer, said voids having a filler therein to oppose a change in volumeand inhibit relative axial movement between said pipe and saidconnector, wherein said conical member is connected to a flange forconnection to said fitting, and wherein said inner layer includes aliner that extends through said flange and across a face thereofopposite to said fitting and radially from the axis of said pipe saidinner layer being restrained by said fitting and said flange.
 18. A pipeassembly according to claim 17 wherein a filler is located between saidinner layer and said conical member.
 19. A pipe assembly according toclaim 18 wherein said filler is hardenable after insertion.
 20. A pipeassembly according to claim 20 wherein said filler is a thermosettingpolymer.